so I now need to get an sdhc reader... does it matter which I get as long as it is usb2 and has transfer rate of 480Mbps? the class 6 cards are max 6MB/s anyways.
I have seen them for $10 up to $35 does it make a difference which I get?

I got a 2 dollar one on ebay, and it works fine. Get them from a US or Hong Kong Seller, a us seller you will get it in a week, hong kong about 2.5 weeks. Actually most class 6 cards have read speeds faster the 6mps. That is why if you look at the sandisk Ultra it said 15mb read/write combine. The read speed is always faster then write speed.

Class 6 SDHC cards have a minimum writespeed of 6 MegaBytes per second.

That's minimum speed; they can be faster.

That's write speed; reading is faster than writing.

USB has a maximum throughput of 480 MegaBits per second, but that can change based on one or more devices connected to a single USB Controller. The slowest device connected to a USB controller sets the maximum speed for all the other devices on that controller. Also, USB is a half-duplex communication protocol, so while the maximum throughput is 480Mbps, at half-duplex, that's a functional throughput of as little as 240 Mbps, and that's if there are no other devices connected to the controller. A card reader with a maximum throughput of 6 MegaBytes per second would slow down all the other USB devices you've got connected to the USB Controller. And the more devices connected to the USB Controller, the more bandwidth the controller must devote to communicating with the other devices, even if they have nothing to say. And, again, all that communication will only take place at the maximum speed of the slowest device.

so in practical terms the difference is the speed correct? how much of I difference will I see with a 4GB or 8GB card? I will probably not wait til they are full to download - probably will download maybe a gig at a time... realistically if a gig can hold about 250 photos...
What kind of a practical difference are we talking about?

True, transferring a few hundred photos occasionally won't make much difference. But a slow USB device has the potential of slowing down your computer as long as the slow USB device is connected to it (depending on what other stuff you've got connected to it.) If you connect your mouse to the same USB controller as an external hard disk drive, the mouse will cause the hard disk drive to perform poorly.